The present invention relates to the preparation of new N-cyano-formamidines having the formula I: ##STR2## wherein R is 2-[[(5-methyl-1H-imidazol-4-yl)methyl]thio]ethyl, 2-[[[5-(dimethylamino)methyl]-2-furanyl]methyl]thio]ethyl, 2-[[[2-[(aminoiminomethyl)amino]-4-thiazolyl]methyl]thio]ethyl or 3-[3-(1-piperidinylmethyl)phenoxy]propyl, as well as the non-toxic addition salts such as hydrochloride, dihydrochloride and acid maleate.
The compounds of the present invention may be obtained in accordance with the following reaction: ##STR3## wherein R is as defined above and R.sub.1 is a linear or branched alkyl group having 4 carbon atoms at most, preferably ethyl.
The reaction is carried out at room temperature in a medium selected from acetonitrile or an alkanol having 1 to 4 carbon atoms, preferably ethanol. When the amines of the formula III are not used in free form but salified with mineral acids, such as the hydrochlorides or dihydrochlorides, it is convenient before starting reaction with N-cyano-formimidate (II) to neutralize the acid by addition of either an organic base, preferably triethylamine, or an aqueous solution of alkaline or alkaline-earth carbonate or bicarbonate, preferably potassium carbonate.
It is known that histamine, a physiological compound which is found in living organisms, may be bound to certain specific receptors for exerting its activity. Two classes of histamine receptors have been identified so far: H.sub.1 -receptor (Ash and Schild: Brit. J. Pharmac., 20, 427, 1966), in which histamine activity is blocked by the conventional antihistaminic drugs like mepyramine; and H.sub.2 -receptor (Black et al., Nature, 236, 385, 1972) in which histamine activity is blocked by cimetidine. The blockade of histamine activity over H.sub.2 -receptors results in the inhibition of gastric acid secretion, thus making the compounds with this potency effective for the treatment of peptic ulcers and other pathologies causes by or stimulated by gastric acidity.